Punch tool assemblies for use in turret punch presses typically include a punch, a punch holder attached to or formed integrally with the punch, a guide for housing the punch and punch holder, a stripper plate having a central opening for receiving the tip of the punch seated in and connected to a top end of the guide, a two-piece punch driver connected to the punch holder, and a compressible spring disposed around the punch driver and abutting the bottom end of the guide. Over time, the punch tip becomes dull and must be sharpened. The sharpening process requires releasing the stripper plate and removing the punch, the punch holder and possibly the punch driver from the guide. Such sharpening reduces punch height, thereby requiring punch adjustment when the assembly is reinserted in the guide. In addition to sharpening, removal of the stripper plate and replacement of the punch is also required when a different punch hole configuration is desired. Such assembly operations, which typically require the use of wrenches, screwdrivers, shims and the like, are time intensive and tedious. Release and adjustment mechanisms are needed for punch tools to facilitate the punch sharpening and replacement operations by eliminating the need for special tools and for such mechanisms that are easily manipulated under workplace conditions.
Previous attempts to provide for quick release of the stripper plate have proven unacceptable. U.S. Pat. No. 4,248,111 to Wilson et al. shows a stripper plate release mechanism in which clips having holding tabs engage a groove in the stripper plate. A separate fork-shaped tool slides into a groove and forces the clips outwardly, thereby disengaging the holding tabs. U.S. Pat. No. 5,301,580 to Rosene et al. describes a locking ring stripper plate assembly which includes a rotatable stripper plate cap which is manually rotatable with respect to the guide sleeve. The stripper plate is released by rotating the cap to loosen a split end retaining wire. A spring-loaded locking button locks the rotatable stripper plate cap in position. U.S. Pat. No. 5,127,293 to Chatham shows a stripper plate which is held in place by a retaining ring having locator slots and retaining projections and hence is keyed for released and locked operation. A plunger assembly is mounted on the guide assembly and includes a spring-biased plunger that is reciprocal in a direction substantially parallel to the longitudinal axis of the guide assembly. Other patents related to stripper plate release mechanisms include: U.S. Pat. No. 3,521,911 to Hanes et al., U.S. Pat. Nos. 4,446,767 and 4,092,888 to Wilson, U.S. Pat. Nos. 4,989,484, 5,056,392 and 5,081,891 to Johnson et al., and U.S. Pat. No. 2,491,128 to Nelson. None of those patents provide for quick release of the stripper plate without major disassembly of the punch tool assembly or contemplate the easily manipulated stripper plate retaining means of the present invention.
The punch release mechanisms documented in the prior art have also proven ineffective. U.S. Pat. No. 4,577,875 to Miyakawa describes a removable tool fastening assembly wherein a tool shank is retained in a bore of the spindle by ball bearings positioned in through-holes of a tubular member. To release the shank, a slidable sleeve having an annular recess slides forward so that the ball bearings are released from engagement. An ejector member is used to push the punch out of the bore. U.S. Pat. No. 5,037,254 to Asberg describes a tool clamping device having a conical arbor intended to carry a tool. The conical arbor includes a rear portion having a threaded bore in which a draw tap is threadably engaged. The draw tap is provided with an annular recess for receipt of a locking ring located in a clamping sleeve. The conical arbor is released by exerting a press force on the draw bar sufficient to press the draw bar and sleeve axially forward, thereby enabling the locking ring to expand radially outward and releasing the draw tap. U.S. Pat. No. 4,777,714 to Blessing describes a quick-change mount for chucks comprising a servo-actuated drive sleeve with a clamping sleeve located within and rigidly attached to a piston rod. The clamping sleeve includes an annular series of holes with balls provided therein. The sleeve is spring-biased so as to force the balls inward, displacing them into the annular groove of the clamping jaw carrier, thereby securing the carrier in place. The clamping cylinder and the sleeve transmit a clamping force to the carrier. U.S. Pat. Nos. 3,548,700 and 3,595,113 to Herzog et al. describe a punch holder and drive assembly including a complex cage, pin or sleeve assembly for maintaining ball bearings in engagement with a shank extending from the punch. Japanese Patent JP 6-99302 describes a tool holding assembly wherein a stud having a shoulder region is releasably secured by ball bearings. Elastic members urge adjacent members upward when the lock is released, causing the ball bearings to move radially inward and slightly upward. U.S. Pat. Nos. 4,850,755, 3,720,417, 3,735,993, 3,633,931, 3,658,351 and 4,309,042 describe quick release ball-lock mechanisms including a ball sleeve and an axially slidable locking collar. None of the prior art references teach or suggest a punch release mechanism whereby simply pressing down on the assembly releases the punch.
Regarding punch tool height adjustment, numerous patents show the use of threaded parts for effecting height adjustment, but none disclose an easily operable locking means for controlling relative rotation. U.S. Pat. No. 5,647,256 to Schneider shows a punch unit that provides for the adjustment of the total length of the punch in arbitrarily small steps. The lower punch driver element has a threaded bore into which the threaded shaft of upper punch driver element can be screwed. The punch driver element and punch are fixed against relative rotation by means of a spline that engages an axial linear groove in the guide bushing. To change the height of the punch, a push button must be depressed to unlock the base of the punch driver element, thereby allowing the punch driver element to rotate and effect a change in the position of the punch. U.S. Pat. No. 4,375,774 to Wilson et al. shows an adjustable punch assembly wherein the punch head includes a threaded post disposed axially downward for threadable engagement with the threaded wall of the punch driver. Bolts affix the punch head to the spring support collar. Expandable locking pins are positioned in cavities provided in the punch head and the punch driver for preventing undesired rotation of punch head about the threaded connection with respect to the punch driver. To adjust the height of the punch, the operator removes the assembly from the guide, removes the locking pins, rotates the assembly with respect to punch driver, and then returns the assembly to the guide. Adjustments in height are only possible when the punch assembly is removed from the guide assembly. U.S. Pat. No. 5,329,835 to Timp et al. shows an adjustable length punch set comprising a punch holder and a replaceable punch blade disposed within a punch sleeve. The punch holder has a threaded male portion which screws into a threaded female portion of the punch driver. The length adjustment mechanism consists of a push button and a biasing spring seated in the extension of the cavity such that it cannot be rotated with respect to the punch holder. The push button is held in engagement with the punch driver by a set of detent stops. This arrangement locks the punch driver to the punch holder to prevent rotation. To make an adjustment, the operator depresses the adjusting length push button through the adjacent hole to release it from engagement with the detent stops. Simultaneously, the operator rotates the punch driver and the spring with respect to the punch holder. U.S. Pat. No. 5,131,303 to Wilson et al. shows a punch assembly that includes a punch holder having a female threaded end and a punch body having a male threaded end that is matingly received within the female end of the holder. As the punch holder is rotated with respect to the punch body, the punch body moves axially with respect to the punch holder. An arcuate wire clip locks the threaded ends against relative rotation. None of the prior art references provide for easy and precise punch height adjustment when the tool is fully assembled in the housing and for locking means disposed between the punch head and the driver sleeve.
Accordingly, it would be desirable to provide a punch tool assembly wherein the stripper plate and punch may be rapidly removed without the need for tools, wherein the height of the punch may be adjusted in the guide, and wherein the assembly and adjustment operations require limited manual dexterity.